Mercury boiler



May 16, 1939- w. L. R. EMMET 2,158,856

MERCURY BOILER Filed May 17, 1935 4 Sheets-Sheet l May 16, 1939. w. L. R. EMMET MERCURY BOILER Filed May 17, 1935' 4 SheetsFSheet 2 Inventor: William LR. Emmen,

W. L. R. EMMET May 16, 1939.

MERCURY BOILER l(Sheets-Sheet 3 Filed` May 17, 1935 Inventor: William L, R Emmet, b9 E. His Attorney :May 16, 1939. w., L. RfEMMET MERCURY Holman Filed May 17, 4 Sheets-Sheet 4 Inventor Willim LA?. hrhet `H is Attovneu.

Patented May 16, 1939 UNiTED STATES PATENT OFFICE.

MERCURY BOILER tion of New York Application May 17, 1935, serial No. 22,119'

9 Claims.

The' vpresent application is a continuation in part of my application Serial No. 691,133, led September 27, 1933'. The invention relates to mercury boilers and has for its general object the provision of an improved construction and arrangement of mercury boilers in which a comparatively small' amount of mercury liquid is necessairy to' operate the boiler and in which the' liquid may be heated to high" temperature without endangering the heating elements for conducting' the fluidi through the combustion chamber or chambers of the boiler.

The problems met with in the use oi mercury in boilers are radically different from those appearing in the design of steam boilers; These differences are partly due to the different physicala characteristics oi mercuryv and water and partly due tov the high cost of the iirst. Mercury has high density, high surface tension, low specific" and latent heat, and littletendency toi wet steel or ironf surfaces.

The di'iierent characteristics between` mercury and water lead to different boiler designs and it is important telnet-e that certain apparent similari'- ti'es and equivalents of the two` kinds of boilers areactuallyr fundamentally different because `such seeming equivalents are provided andsuggested for different reasons, or from another view-point, serve different purposes inthe two` cases. After an extensive study of the mercury boiler design, l? have foundy that better results, better economy and eiiiciency are obtained" with comparatively smallV boilers or heating units thanV with large ones. Therefore, in accordance with my' invention, I sub-divide a large boiler into a plurality of' smaller units having independent sources of heat and arrangethern so that they may be operated individually or collectively. Each unit comprises a` plurality ofl tubes having upper ends connected tca drum and being arranged to form a substantially cylindrical combustion chamber. The source of heat supply is preferably provided near the lower part ci the chamber. The proclucts orc'ombustion then pass upwalol through the chamber and thereby deliver the heat energy through the tubes to the mercury therein. Since the temperature range in which'heat is delivered to=v the' mercury is high comparedv with that in steam boilers, andil since the rate of radiation varies-'withthe fourth power of the absolute temperature; a relatively large proportion of the heat' energy produced in the combustion chamber can be delivered by radiation. In my improved boiler arrangement, extreme application is made ofthis-eature in` that at least 757 per cent of the heat energy is delivered inthe form' of radiant heat to the tube elements. To make this possible, the height cil theV combustion chamber is made at least twice that of its maximum diameter so that the mercury liquid which is supplied to the lower ends' oi the tubes reaches its boiling temperature and is' vaporized in the upper portions only of the tubes. This is important because liquid mercury contained in the lower tube portions permits a much higher heat transfer than' were a mixture of liquid and vapor contained in these lower portions. From another angle, I provide a boiler in which the vapori'zationJ zone' isA shifted to a high level in the combustion chamber. In such an arrangement with the source' oi heat supply in the lower end of the combustion chamber, a very highheat transfer taires place through the lower tube portions, and the transfer of heat decreases toward the upper ends oi the tubes. This decreaseof heat transfer however does not endanger the upper tube portions by excessive rise in ternperatures because the radiation towards said portfionsis much less than towards the lower portions.

For a better understandingv of the above and other features of my invention, attention is directed to the following description and the claims appended thereto in connection with the accompan-ying drawings.

In the drawings, Fig. 1v represents a sectional front" View ofy a boiler embodying my invention; Fig. 2isa sectional top View of a boiler arrangement;` Figs. 3 ande illustrate'to an enlarged scale certain parts of Fig. 1; Fig. 5 is a diagrammatic illustration ofl a boiler embodying my invention; Fig. Bis a sectional View of a modication ernbodying my invention; andV Figs. 7 and 8 are detail View of Fig. 6; Fig. 9 is a sectional view of another modification oi my invention; and Figs. l() andi ll are perspective detail views of Fig. 9.

The Aboiler comprises a plurality of heatingunits Ifllfand il (Fig. 2) arranged in a chamber or furnace having a wall it" and a` partition i5 separating the units lla-and ll to dei-lne two' groups. Each unit includes a preheater il connected by a conduit lttoalioluid supply header lil' `(l'ig. 5) and bya conduit 2li-to the boiler proper 2 l Each boiler proper or unit has a vapor discharge conduit 22 connected to a vapor header 235 (Fig 5). Provided in the liquid supply header and in the vapor dischargeheader arevalves 2d and lirespectively for disconnecting theindividual units to operatethe power plant with varying numbers or unitsn in accordance with the load demand.

This permits the operation of a power plant at maximum eiiiciency;

Referring now to Fig. 1 where I have shown more in detail the arrangement of a heating unit, together with a preheater for the unit, the unit comprises an outer cylindrical or tubular wall 23 made of reproof material. The term cylindrical is used in a broad meaning and not limited to a structure having an annular or circular cross-section. A plurality of tubes 21 are vertically arranged to line the interior of the wall 26 and held in position by means oi hoops or rings 28 embedded in the wall. Each tube is fastened to the rings by welds 2Q (Fig. 4). The spaces dened between adjacent tubes are filled with insulating material Sil and the outer surface of the wall 2S is covered by a metal sheet 3l.

In manufacturing the structure above described I preferably Weld first the tubes to the hoops 28 and thereafter provide the wall 26 and the metal covering 3|. The tubes, together with the outer wall, form a combustion or radiation chamber or space 32. The lower ends of the tubes are connected to an annular header 33 and the upper ends of the tubes are connected to a drum 34 concentrically located above the out'er wall 26 of the unit, the upper ends of the tubes being bent inwardly at dierent angles or degrees and have their ends projecting into substantially uniformly distributed openings in the lower curved portion of the drum 34. The drum is provided with a head 35 held in position by locking means 3G and sealed by a ring 31, more fully described in my Patent 1,902,494, Iiled September 17, 1928, and assigned to the same assignee as the present application. As pointed out above, the upper ends of the tubes are spaced from each other dening thereby intermittent spaces through which gases formed in the combustion chamber may escape.

A displacement or iiller block 38 having openings 39 (Fig. 3) is provided within the lower portion of the drum and held in position by means of stops 4 fastened to the wall of the drum. Each opening 39 of the filler block is in alignment with an opening in the bottom of the drum. A sleeve 4! inserted in the recessed upper end of each tube 21 projects into the opening 39 oi the displacement block. A tubular member 42, forming in substance an extension of the tube 21 is fastened to the displacement' block by a weld 43 and extends above the liquid level in the drum. Fluid expelled from the tube 21 is conducted through the sleeve 4! into the tubular member 42 whence it is expelled from the upper end thereof. In order to prevent the liquid expelled from the tubes 42 from iiowing together with the discharged vapor into the discharge conduit 22, I provide on top of each tubular member 42 a liquid-vapor separating and liquid-reversing device, in the present instance shown as a cap 44, opening in a downward direction and having an edge portion fastened t'o the end face of the tubular member 42. The opening of cap 44 is considerably wider than the opening of the tubular member 42.

During operation, liquid discharged from the tubular member 42 is directed along the inner surface of the cap and reversed, to be expelled from the cap in a downward direction, as indicated by an arrow 45 (Fig. 3). Vapor discharged from the tubular member 42 does not follow the inner curvature of the cap owing to its lower gravity, but escapes in a sidewise direction from the lower end of the cap opening whence it rises toward the discharge conduit 22 as indicated by an arrow 46. It is important to note that the tubular member 42 has an inner diameter which is equal or smaller t'han the inner diameter o1' the tube 21. rihis causes the iiow of uid from the tube 21 into the tubular member 42 being discharged at high velocity, resulting in a better separation of liquid from vapor and a better circulation of fluid.

Liquid is conducted from the drum to the lower header by means of conduits or tubes 41 arranged outside the wall 2G. These tubes with regard to the downward direction of the flow of fluid therethrough may be termed down-tubes, whereas the tubes within the combustion chamber 32 may be termed up-tubes. In the present instance, I have shown four down-tubes 4? having their upper ends connected to a central downwardly projecting portion 49 of the drum. The portion 49 forms an extension oi a central bore in the displacement block and denes a manifold to which the down-tubes 41 are connected. In order to obtain uniform flow of liquid from the drum 35 to the lower header 33, the down tubes are symmetrically spaced and have in the present instance their lower ends branched into two branches Eil and 5i connected to the annular header 33. Thus, the four down-tubes have eight branches connected to points of said header 45 angular degrees apart. The upper ends of the down-tubes 4l" are covered with lagging 52 to prevent heating of liquid flowing therethrough by the gases escaping from the combustion chamber.

Liquid is conducted to each drum from the preheaters 'i comprising an inlet header 53 receiving liquid from the conduit i3 and an outlet header 54 discharging preheated liquid through he conduit 2Q to the drum. The two headers are connected by a plurality of hairpin-shaped tubes 5E. The preheater is located in the upper space of a conduction or gas chamber 56 dened between the wall 26 of the boiler proper and a partition or baille 51. To utilize the heat energy remaining in the gases discharged from the combustion chamber after they have passed the preheater, I niay provide in the lower portion of the conduction space another heating means, in the present instance indicated as a steam broiler 58 comprising an inlet header 59 receiving water from any suitable source, not shown, and an outlet header l connected to the inlet header 59 by 5 a plurality oi tubes 6| and provided with a steamdischarge tube or conduit' 62.

Fuel to be burned in the combustion chamber is supplied through a burner 83 provided in a central opening in the bottom oi the combustion i chamber. Air for maintaining the combustion is conducted to the space around the burner by a conduit 54 connected to an air preheater 65 having an inlet GG and being located in the lower part of a flue dened by the outer furnace wall I5 and the partition 51.

During operation, liquid is conducted through the preheater i1 to the drum of the boiler proper, whence the liquid flows through the down tubes 41 and the lower hea-der 33 into the up-tubes 21. The liquid is heated and partly evaporated in the up-tubes and expelled into the drum where the vapor is separated from the liquid and discharged through the conduit 22. The liquid expelled from the up-tubes into the drum is recirculated through the down-tubes and the lip-tubes. Each liquid particle is circulated many times from the drum through the downand up-tubes until it is evaporated. The circulation of liquid permits the operation of the boiler or generator at high temperatures without endangering the fluidconducting elements or up-tubes in the combustion chamber.

The circulation of the fluid in the arrangement just described takes place by gravity; that is, t'he liquid contained in the down-tubes 41 forces the mixture of liquid and vapor contained in the up-tubes up into the drum. The heating unit is preferably built standard size. This permits the manufacture of an elastic fluid-generating plant with any desirable output by the provision of a suitable number of standard heating units. Another advantage of the arrangement is, as pointed out above, that the heating units may be operated individually and collectively. Thus, in the present arrangement, where the generators comprise six units, three or less units may be operated at one time.

In the arrangement described herein the heating tubes are substantially entirely filled with mercury liquid during starting operation. A small amount of liquid may even be contained in the drum. In order to reduce the time necessary for starting the boiler, it is desirable to remove a portion of the liquid from the heating tubes, that is, to lower the cold liquid level therein as far as possibie Without endangering the empty tube-portions due to excessive heating during starting. Also, I have found it desirable to iilter the mercury liquid conducted to the lower ends of the heating tubes in order to remove undesirable sub stances such as dirt therefrom. Such substances may cause clogging of the heating tubes as well as the down-tubes conducting mercury to the lower ends of the heating or up-tubes. This is accomplished in accordance with my invention by the modied arrangement shown in Figs. 6 to 8.

This arrangement comprises a plurality of uptubes or heating tubes il@ having lower portions 8| arranged to form a cylindrical combustion chamber 82 having a height of more than twice its diameter. Intermediate portions 83 of the heating tubes are bent inwardly at various angles and degrees and upper portions tft forming continuations of the intermediate portions are arranged in parallel relation to form a plurality, in the present instance four rings or rows of tubes substantially uniformly spaced apart. A baffle t5 of heatresisting material is held between the inner ring or row of tubes to prevent combustion gases from escaping along the cylindrical space defined by this inner ring of tubes or, from another viewpoint, to cause combustion gases to now through the intermediate spaces defined by the bent or neoked-in intermediate and upper portions of the heating tubes. The lower and intermediate portions of the tubes line a refractory Wall 86 corresponding to the wall 2t of Fig. l. The tubes are securely held on this wall by hoops or rings 81 embedded in the wall and welded to the tubes.

The outer surface of the wall et is covered by' sheet lining 88. The tubes when assembled form a bottle-shaped structure with a necked-in porn tion having an upper end to be connected to a drum or upper header and an open bottom to accommodate a source of heat as will be described hereafter. The lower ends of the tubes are conh nected to a' header 39 which in the present instance is protected from radiant heat by a refractory wall 9u. The latter, together with the outer sheet metal 83 form an annular chamber 9| readily accessible to permit repairat thelower ends of the tubes and also if necessary cleaning of the header 89. Fuel and air are conducted to `the lower end of the combustion chamber by means including a burner 92 and an air conduit 93 corresponding to elements 63 and 64 respectively of Fig. 1. All of the mercury heating tubes are exposed to radiant heat and the major portion, preferably at least 75% of the total heat produced in the combustion chamber is transmitted to the tubes in the form of radiation. The upper ends of the heating tubes are connected to a drum 94 having an axis in alinement with that of the combustion chamber. As stated before, these upper ends of the heating tubes are uniformly spaced apart and, as shown in the drawings, they are inserted in uniformly spaced openings extending substantially over the entire area of the bottom wall of the drum 94.

Fluid, that is, mixture of mercury liquid and vapor, is discharged from the upper ends of the heating tubes into the drum through the intermediary of liquid vapor separting means. These means include a nozzle member 95 for each tube end. The nozzles 95 are fastened to the tube ends and extend into the lower ends of ducts formed by a plurality of tubes 96 held on a perforated plate 9T. The plate 91 is secured to the drum by bolts 98. The nozzles 95 are disposed below the normal liquid level in the drum and the upper ends of the tubes 96 extend above the normal liquid level. The upper ends 99 of the tubes 9G, as can best be seen in Fig. 7, are curved and arranged to discharge uid laterally in a somewhat tangential direction towards the cylindrical inner surface H30 of the drum 94. The inner row of tubes 96 is higher than the outer rows. In the present instance the ends of the four rows of tubes s6 are disposed on a conical surface and the discharge ends 99 oi these tubes are arranged so that the streams discharged therefrom do not interfere with each other, each end 99 discharging a stream directly towards the wall surface lull. This arrangement results in an ejector action at the top of the nozzles and causes mercury surrounding the nozzles 95 to be picked up by the discharging stream of liquid and vapor. This action results in a relatively low velocity discharge of liquid in the form of large drops or clots in contrast to a nely divided high velocity spray occurring without the lejector action. The plate 91 as shown is spaced somewhat from the adjacent surface of the bottom wall so that mercury may freely flow to the ends of the nozzles 95, causing an ample supply of liquid to the discharge ends of the nozzles 95, which liquid is picked up by the streams discharged from said nozzles. By this arrangement the discharge of nely divided mercury liquid is eliminated. This is an important feature of myarrangement. Extensive experiments have shown that the discharge of liquid in the form of a finely divided spray is undesirable because such line particles are apt to be picked upby the vapor and and discharged by the boiler to turbines or other parts to which vapor is conducted. 'Ihe carrying-over or discharge of liquid even in very small quantities is highly objection.- able not only because the presence of liquid in the vapor impairs the efficiency of a turbine or other apparatus to which the vapor is conducted, but also because it tends to hasten the loss of certain alloys associated with the mercury in present day mercury boilers. Such alloys, like sodium or aluminum, are mixed with the mercury to inc crease the rate of heat transfer to the boiler heating elements and also to reduce the dissolving of iron or like metal from which the boiler walls are made by the action of mercury in contact therewith. In View of these facts the .complete absence of priming or carrying-over of liquid becomes more important in a mercury boiler than in boilers using water or other liquid as operating substance.

Whereas the head 35 of Fig. l is secured to the drum by means described in my aforementioned Patent No. 1,902,494, I provide in the` modiication of Fig. 6 another improved arrangement for securing a head to a drum. As shown in Fig. 6, the upper part of the inner surface of the drum 95 is recessed to form a shoulder IOI. The upper end of the drum has an elliptical-shaped opening |02. An elliptical head |03 with a shoulder |04 engages the shoulder |0| formed on the recessed inner wall of the drum. During assembly the elliptical head |03 is put into the elliptical opening of the drum and after it is inserted it is turned through ninety angular degrees.

Fig. 7 shows the elliptical head in its relative position to the elliptical `drum opening during assembly. As will be readily understood, the height of the recessed portion of the inner surface must be sufficient to permit insertion and assembly of the elliptical head. The head is held in position and forced towards the shouldered portion of the wall 94 by means including studs |05 secured to the head, and connected to a plate |06 by means of nuts |01. The plate |06 engages the upper face or edge of the drum so that tightening of the nuts |01 causes the head to be forced into close engagement with the shoulder IOI on the drum 94. The bolts |05, as shown in the drawings, are preferably spaced from the edge of the top plate |06 so that the springing action of the top plate will maintain a constant upward pressure on the engagement joint between the head and the drum even when there is no pressure or a negative pressure in the drum. 'Ihe top plate |06 and the head |03 form a space or chamber |08. This space is preferably maintained under a negative pressure, that is, a pressure below atmosphere. This may be accomplished by means including a conduit |09 for connecting the space or chamber |08 to a boiler draft. With this arrangement all leakage of mercury is drained into the suction space |08 and can be condensed and saved. In certain instances it is desirable to maintain within the space |08 an atmosphere of inert or decxidizing gas such as hydrogen. In the present instance I have shown a pipe |I0 for conducting a deoxldizing agent to the suction chamber |08.

Mercury vapor is discharged from the drum by a discharge conduit I connected to the upper end of the vapor space. The discharge of liquid mercury particles is further reduced by the provision of a plate ||2 having a bent edge secured to the inner surface of the drum by bolts I I3 and a central opening I I4 forming a path for the mercury vapor to be discharged. As stated before, I provide means for reducing the mercury liquid level during starting or, from another viewpoint, maintaining the mercury liquid at a low level when cold and means` for filtering the mercury liquid before it is conducted to the lower ends of the heating tubes.. These means include an auxiliary drum ||5 disposed external the combustion space and having a` bottom I I6 located at a level substantially below the desired cold liquid level in the heating tubes. The drum has a cylindrical wall ||1. A recessed head portion IIS having an elliptical opening I I9 is secured to the upper end of the wall II'I by a weld |20. The elliptical opening of the auxiliary drum is closed by means including a header |2I and a top plate |22 arranged in similar manner as the head |03 and the top plate |06 of the main drum 94. A negative pressure is maintained within the space defined between the head |2| and the top plate |22 by means including a suction conduit |23 communicating with said space. The auxiliary drum receives mercury liquid from the main drum 94 through a conduit |24. Mercury liquid may be conducted to the auxiliary drum from another source, for instance, a mercury condenser in the case of a power plant through means including a conduit |25 connected to the conduit |24. Mercury liquid is discharged from the auxiliary drum through a conduit |26 connected at its upper end to the bottom of the auxiliary drum and at its lower end to the header 89 by a connecting box |21. A retaining member |28 in the form of a bale, a screen or the like, is disposed in the lower portion of the auxiliary drum for retaining large pieces of solid material within the auxiliary drum or, from another viewpoint, for preventing large pieces of solid material from entering and clogging the down-tube |26. The retaining or filtering member |28 is secured to a rod |29 extending into the upper portion of the drum and having an arm |30 secured to the wall I|"| by bolts |3I. With this arrangement the retaining member |23 and solid material collecting thereon may be easily removed from the auxiliary drum after disassembly of the head |2I. If desired, the auxiliary drum may be used also as a means for feeding certain ingredients, such as aluminum, sodiurn or the like, to the boiler. Such ingredient when supplied in the form of solid rods or pieces dissolves gradually within the auxiliary drum, whence it is carried into the heating tubes of the boiler. When cold, the boiler is lled with mercury |32 to a level indicated by the dash-dotted line |33. The level |33, as shown in the drawings, is below the upper end of the combustion chamber. Thus, the portion of the heating tubes disposed above the level is empty during starting operation. This permits quick starting due to the relatively small static head acting on the mercury within the lower ends of the heating tubes. During starting the mercury due to expansion rises within the heating tubes to a level above that of the plate 9'! in the main drum, whence the liquid is discharged through the conduit |24 to the auxiliary drum to be recirculated through the heating tubes. As pointed out before, the velocity of the mixture discharged from the upper ends of the heating tubes through the nozzles 95 is considerably reduced due to the fact that said nozzles are normally immersed in mercury liquid. The streams of the mixture are discharged laterally from the upper ends of the tubes 96 towards the inner surface |00 of the drum whereby the liquid content of the mixture having high inertion is forced outward towards the surface |00 and the vapor content of the mixture having less inertion escapes towards the center or the drum through the opening I I4 to the discharge conduit III.

The arrangement shown in Fig. 9 comprises a drum |420 covered with lagging Uil. The drum has a bottom |42 with a reinforced or heavier central portion |43. A cylindrical wall |44 is secured to the bottom portion |42 by an annular weld |45, A plurality of annular rows of heating tubes |46 is connected to the bottom. The tubes project through openings in the bottom and have their upper ends united with the adjacent bottom portions by fused metal |47. The arrangement of the lower portions of the heating tubes and the combustion chamber may be the same as that described above with respect to Figs. 1 to 8.

The boiler of Fig. 9 includes an improved arrangement for securing and sealing a head to the drum. In accordance with my invention, an annular head |48 is screwed into a threaded portion |49 of the cylindrical wall |44. The drum and its head are of comparatively light construction. For this reason the head |49 is directly fastened to a central bottom portion |43 by means of a bolt |50 secured to the portion |43 and projecting through a central opening in the head |48. The central portion of the head |48 is forced inward, that is, in the direction towards the bottom by means of a nut on the outer end of the bolt. Thus, the provision of the bolt permits safe operation at high pressure with a comparatively light drum structure. In order to prevent leakage of iiuid along the threaded portion of the head and along the bolt, means are provided to completely seal the head to the drum and also to prevent leakage along the bolt. The means for sealing the head to the cylindrical wall |44 comprise a ring |52 secured to the outer surface of the head |48 by a weld |53 and another ring |54 welded to the upper face of the cylindrical wall |44. In the present instance the outer portion of the ring |52 overlaps somewhat the threaded portion of the wall. A cylindrical sheet |55 is secured to the outer edge of the ring |52 by means of a weld |56, and another cylindrical sheet |51 surrounding the sheet |55 is secured to the ring |54 by means of a weld |58. The upper ends or edges of the sheets |55 and |51 are united, in the present instance by a weld |59. Thus, the two sheets form a narrow, annular space receiving all the leakage of fluid passing along the threaded portions of the head and the cylindrical wall and preventing any leakage to the atmosphere.

During manufacture, the inner ring |52 and the sheet |55 are secured to the head |48 after the latter has been fastened to the wall |44. Thereafter the outer ring |54 and the cylindrical sheet |51 are secured to the cylindrical wall |44. Finally, the upper edges of the two cylindrical sheets are united.

As the pressure in the space or chamber de fined between the two cylindrical sheets may assume high values during operation, means are provided to prevent bursting of these sheets or, from another viewpoint, to limit the radial distance between the cylindrical sheets. This means in accordance with my invention comprises two rings, an inner cylinder or ring |90 placed on top of the inner ring |52 and closely spaced with the cylindrical sheet |55, and an outer cylinder or ring |6I placed on top of the outer ring |54 and surrounding in closely spaced relation the outer cylindrical sheet |51. Thus, the two cylinders or rings |69 and 6| are loosely placed on top of the rings |52 and |54 respectively to form an annular space for accommodating the cylindrical sheets |55 and i51 and preventing bursting of these sheets during operation.

The arrangement for sealing the upper end of the bolt to the head |48 is similar to the one just described. The upper end of the bolt and the nut are surrounded by a wall |62 secured to the head |48 by a weld I6. A head |64 is screwed into an upper portion of the wall |62. The wall |62 and the head |64 dene a chamber |65 for receiving leakage passing along the bolt 50. The means for preventing leakage from this chamber to the atmosphere include a ring |66 with a cylindrical sheet |61 secured to the head |64 and a ring |68 with a cylindrical sheet |69 surrounding the cylindrical sheet |61 and secured to the wall |62. From another Viewpoint, the rings |66 and |68 may be considered reinforced anges of the cylindrical sheets |61 and |69 respectively. The upper ends of the sheets are united by a weld |10. The two sheets form a narrow space for receiving leakage passing along the threaded portion of the wall |62. The two cylinders or rings |1| and |12 placed on top of the rings |66 and 68 respectively form an annular space |13 for accommodating the cylindrical sheets and for limiting the expansion of the sheets, that is, of the space dened between them.

The sealing arrangement above described is simple in design and may be manufactured at low cost. An upper portion of the drum, forming a vapor space is connected to a vapor discharge conduit |14 and a lower portion of the drum normally filled with liquid is connected to a liquid discharge conduit or down-tube |15.

Another important feature of the construction shown in Fig. 9 is an improved arrangement for discharging a mixture of mercury and vapor from the tubes into the drum and for separating this mixture to prevent discharge of liquid through the vapor discharge conduit |14. This means comprises a lower cage |16 and an upper cage |11. The lower cage |16 has an outer cylindrical wall |18 closely spaced with the inner surface oi the drum, an inner cylindrical wall |19 closely spaced with the central bottom portion |43 and an intermediate cylindrical wall |80. Deilectors or baffles |8| are `fastened to these walls and arranged so that adjacent baflles |8| together with adjacent portions of the walls or rings form a disn charge channel |82 for receiving the mixture discharged from the upper ends of two radially spaced tubes, an outer tube |83 and an inner tube |84. The space defined by adjacent bailles is normally lled with mercury liquid so that the velocity of the mixture discharged by the heating tubes is considerably reduced and the mercury liquid retained, that is, substantially prevented from passing into the vapor space of the drum. The arrangement of the baffles is such that vapor and some liquid discharged from the upper end thereof assumes a somewhat circular path substantially concentric with the inner surface of the drum.

The lower cage |16 is secured to the wall of the drum by bolts |85. In a preferred embodiment the upper portions of the baies IBI are inclined at an angle of about thirty degrees (Fig. l1) to the horizontal.

The upper cage |11 (Fig. 10) serves to separate liquid particles entrained in the vapor discharged from the lower cage |16. The upper cage oomprises an outer row or ring of baffles |86 and an inner ring or row of baffles |81 arranged in staggered relation with respect to the outer baffles or deflectors. The two rows of bales are connected and held together by means of three concentrically spaced rings |88, |89 and |90. The outer ring |90 is provided with lugs |9I secured to the inner surface of the wall |44 by means 0f screws |92. 'Ihe inner ring |88 is held in concentric relation in the drum by means including a sleeve |93 surrounding the bolt |50 and webs |94 connecting the sleeve with the inner ring |88. The lower end of the sleeve |93 rests on the central bottom portion |43 (Fig. 9). In a preferred embodiment the lower portions of the baiiles |86 and |81 are inclined towards the horizontal at an angle of approximately thirty degrees (Fig. 10) but in opposite direction to the inclination of the upper portions of the baiiies IBI of the lower cage. With this arrangement, liquid particles discharged from the lower cage are thrown against the lower portions of the baffles I86 and |81 of the upper cage and returned to the liquid space.

During manufacture, the lower and the upper cage after being completely assembled are inserted in the drum and secured to the cylindrical wall |44.

Having described the method of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A mercury boiler including a cylindrically shaped refractory wall, a plurality of vertical tubes lining the wall and forming a cylindrical combustion chamber, the height of the chamber being more than twice its diameter, a cylindrical drum located above the tubes, the drum being in alignment with the cylindrical combustion chamber and having a bottom with uniformly spaced openings over its entire area connected to the tubes, a block in the drum for displacing mercury liquid, the upper ends of the tubes being bent inwardly at Varying angles to form intermittent spaces through which gases may escape from the combustion chamber, a source of radiant heat located near the lower portion of the chamber, and conduit means centrally connected to the bottom of the drum for conducting mercury liquid to the lower ends of the tubes, the arrangement being such that at least 75 per cent of the total heat produced is delivered by radiation to all of the mercury liquid filled heating tubes.

2. A mercury boiler including a plurality of heating tubes arranged to assume the shape of a bottle with the lower portions of the tubes forming a cylindrical combustion chamber and the upper portions of the tubes bent inward and uniformly spaced within the entire cross-sectional area of the necked-in portion of the bottle contour, and a cylindrical drum including a displacement block for mercury and a central bottom portion with uniformly spaced-apart openings for receiving the upper ends of the tubes.

3. A mercury boiler including a cylindrically shaped refractory wall, a plurality of substantially vertical heating tubes lining the wall. and forming a cylindrical combustion chamber, the height of the chamber being more than twice its diameter, a cylindrical drum with its axis in alignment with that of the combustion chamber being located above and connected to the tubes, the upper ends of the tubes being bent inwardly at varying angles to form intermittent spaces through which gases may escape from the combustion chamber, a source of radiant heat located near the lower portion of the chamber to radiate heat towards the lower portions of all of the heating tubes, an extension for each tube to discharge liquid and vapor in downward direction at points above the liquid level in the drum, means for conducting mercury liquid from the drum to the lower ends of the heating tubes comprising an auxiliary drum connected between the first named drum and the lower ends of the heating tubes, said auxiliary drum permitting a reducion of the cold liquid level in the tubes to a point substantially below the upper ends of the tubes whereby the starting period of the boiler is reduced, and a conduit connected to the auxiliary drum for supplying mercury liquid to the boiler.

4. A mercury boiler including a cylindrically shaped refractory wall, a plurality of substantially vertical heating tubes lining the wall and forming a cylindrical combustion chamber, the height of the chamber being more than twice its diameter, a cylindrical drum located above and connected to the tubes, the upper ends of the tubes being bent inwardly at varying angles to form intermittent spaces through which gases may escape from the combustion chamber, a source of radiant heat located near the lower portion of the chamber to radiate heat towards the lower portions of all of the heating tubes, means for conducting mercury liquid from the drum to the lower ends of the heating tubes comprising an auxiliary drum connected between the rst named drum and the lower ends of the heating tubes, and means disposed within the auxiliary drum for retaining solid substances there- 5. A mercury boiler including a cylindrically shaped refractory wall, a plurality of heating tubes lining the wall and forming a cylindrical combustion chamber, the height of the chamber being more than twice its diameter, a drum located above and connected to the upper ends of the heating tubes, upper portions of the tubes being bent inwardly at varying angles to form intermittent spaces through which gases may escape from the combustion chamber, a source of radiant heat located near the lower portion of the chamber to radiate heat towards the lower portions of all of the heating tubes, an extension for each tube to discharge liquid and vapor in downward direction at points above the liquid level in the drum, and means for conducting mercury liquid from the drum to the lower ends of the heating tubes comprising an auxiliary drum connected between the first named drum if,

and the lower ends of the heating tubes, said drum acting as a storage tank for mercury to permit starting of the boiler with the heating tubes only partly lled.

6. A mercury boiler comprising a plurality of heating tubes forming a combustion chamber, a header connected to the lower ends of the heating tubes, a drum connected to the upper ends of the heating tubes, the connections between the heating tubes and the drum being arranged f to discharge liquid and vapor from the tubes in downward direction at points substantially above the liquid level in the drum, and means for conducting mercury liquid from the drum to the header including an auxiliary drum having a bottom disposed substantially below the cold liquid level in the heating tubes and permitting starting of the boiler at a liquid level in the heating tubes below the upper end of the combustion chamber.

'7. A natural circulation type mercury boiler including a plurality of heating tubes having lower portions dening a cylindrical combustion chamber, a cylindrical drum disposed above the combustion chamber and having a substantially uniformly perforated bottom connected to the upper ends of the heating tubes, mercury normally filling the heating tubes and part of the drum, means including a down-tube for feeding mercury liquid from the drum to the lower ends of the heating tubes, and a source of radiant heat in the lower part of the combustion chamber for heating the lower portions of all of the heating tubes, the diierence in gravity between the mercury contained in the down-tube and in the heating tubes during operation causing relatively rapid flow of mercury through the heating tubes, the height of the heating tubes and the liquid mercury contained therein being sufficient to prevent vaporization of mercury liquid in the heating tubes below a predetermined level in the upper part of the combustion chamber at the normal operating pressure of the boiler so that radiant transmission to the heating tubes of at least 75% of the produced heat energy does not elTect undue stresses in the heating tubes.

8. A natural circulation type mercury boiler including a plurality of heating tubes having lower portions defining a substantially cylindrical combustion chamber, a substantially cylindrical drum having a Vapor outlet in its upper portion being disposed above the combustion chamber and connected to the upper ends of said heating tubes, mercury normally contained in the heating tubes and partially filling said drum, means including a down-tube extending externally of the combustion chamber for feeding mercury liquid from the lower portion of the drum to the lower ends of the heating tubes, and a source of radiant heat in the lower part of the combustion chamber for heating all of said heating tubes, the diierence in gravity head between the mercury contained in the down-tubes and in the heating tubes during operation causing relatively rapid now of mercury through the heating tubes, the height of the heating tubes and the corresponding head of the liquid mercury contained therein being suflicient to produce a pressure such as to prevent vaporization of mercury liquid in the heating tubes below a level near the upper part of the combustion chamber at the normal operating pressure of the boiler, the major portion of the radiant heat being transmitted through the walls of the heating tubes to portions iilled with liquid mercury as distinguished from a mixture of mercury liquid and vapor whereby the radiant heat is efficiently utilized and undue stresses in the tubes due to poor heat transmission are avoided.

9. A mercury boiler comprising a plurality of heating tubes having lower portions arranged to form a combustion chamber, a source of radiant heat in the lower portion of the chamber to transmit at least 75% of the produced heat energy in the form of radiation to all of the liquidiilled lower ends of the heating tubes, a cylindrically shaped drum vertically disposed above the chamber and having a bottom connected to the upper ends of the heating tubes, a vapor discharge conduit connected to an upper' portion of the drum, a cage including a plurality of deflecting members forming curved channels and being disposed in the drum for receiving and deecting a mixture of liquid and vapor discharged from the upper ends of the heating tubes and causing the mixture to flow in a circular path along the wall of the drum, said cage being at least partly imemrsed in mercury liquid during normal operation of the boiler, and another cage disposed in the vapor space of the drum and including aa plurality of deilecting members obstructing the flow of liquid particles in the vapor space to prevent liquid particles entrained in the vapor from being discharged into the vapor discharge conduit.

WILLIAM L. R. EMMET. 

